Vibrissae
There
are a number of hair sets on flying squirrels that are serve specific
purposes other than insulating and guard hairs. These thicker hairs are
considered "tactile" hairs, and are usually called vibrissae. Complex
nerve bundles under the skin are attached to each hair bulb, and send
tactile information to the brain for processing. The main set of of vibrissae, or "whiskers" on a North American flying squirrel's face are, for their body size, the longest of all squirrels. Why so long? Flying squirrels are nocturnal, and it is thought that long whiskers aid in navigating dark, unfamiliar cavities and their openings. High-speed photography has shown that as a rule, flying squirrels will close, or partially close their eyes just prior to landing, and while gliding through brush that is more dense than normal. Facial muscles move the vibrissae into a forward-facing position, again, likely as a navigation aid. We can only speculate that this behaviour may help prevent eye injury, and that the vibrissae are aiding navigation in some way. See photo below. The main set consists of two groupings, one on each side of the head, situated on either side of the nose. They project outward from the face, and are several inches long. Another, shorter, set of vibrissae are found on the face just above the eyes. Yet another set is found just below the eyes. These two sets of vibrissae are thought to afford some protection to the eyes, but their function is not yet fully understood. There is another set of vibrissae under the lower jaw, and yet another set is found on the forepaws slightly above the wrist joint, which may assist the squirrel in handling objects. Female flyers have a solitary vibrissa attached to each mamma, which helps stimulate milk production when a pup explores that area.  |